This invention relates to cameras, and particularly to electrically controlled shutters.
In a conventional electrically controlled shutter, an exposure is produced by pushing down a shutter release button. This actuates a shutter opening mechanism and opens the shutter. After a predetermined time, an electromagnet actuates a shutter closing mechanism which closes the shutter. The predetermined time is established by duration controlling means such as an RC circuit.
Such shutters normally operate well. However, if the operator forgets to load a battery capable of energizing the electromagnet into the camera, or when the battery has run down, or when the battery is insufficient to operate the electromagnet, the shutter closing mechanism will not function properly.
This misfunctioning occurs in either of two types of electrically controlled shutters. In one type, the shutter release button is pushed down to actuate the shutter opening mechanism and the shutter begins to open. The electromagnet is then energized for an operating time determined by means such as an RC circuit, to keep the shutter closing mechanism inoperative. After the operating time has elapsed, the electric current stops flowing through the electromagnet. This actuates the shutter closing mechanism and the shutter is closed. If the battery in this type of shutter is defective, the electromagnet fails to hold back the shutter closing mechanism and the latter operates immediately after the shutter opening mechanism.
In the other type of electrically controlled shutter the release button again actuates the shutter opening mechanism. This opens the shutter. After a measured duration of time, the electromagnet is energized to operate the shutter closing mechanism. If, in this type of shutter, the battery is defective, the electromagnet will not actuate the shutter closing mechanism after the measured time has elapsed. Thus, the shutter remains open.
An object of the present invention is to improve electrically controlled shutters.
Another object of the invention is to free electrically controlled shutters from the beforementioned disadvantages.
Another object of the invention is to operate the electrically controlled shutter automatically even if the battery of the electrically controlled shutter is defective or non-existent.